Expandable screen utilizing near neutrally-buoyant particles outside of the screen

ABSTRACT

In one embodiment, a wellbore completion method includes disposing an expandable screen into a well bore and disposing a fluid into an annular space between a wall of the wellbore and the expandable screen. The fluid contains a plurality of near neutrally-buoyant particles. The method further includes radially expanding the screen, whereby the near neutrally-buoyant particles exert a force against the wall of the wellbore.

RELATED APPLICATIONS

This application claims the benefit of Ser. No. 60/532,933, entitled“Expandable Sand Screen Utilizing Near Neutrally Buoyant ParticlesOutside of Screen,” filed provisionally on Dec. 29, 2003.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the field of well bore completionand, more particularly, to an expandable screen utilizing nearneutrally-buoyant particles outside of the screen.

BACKGROUND OF THE INVENTION

Sand control is important during completion and subsequent production ofa wellbore that is in hydraulic communication with Earth formationssusceptible to production of solid materials from the formation. Suchformations are known in the art as “unconsolidated” and, if notprotected with suitable wellbore equipment, may produce solid materialsof a character and quantity so as to damage the wellbore, or at leastreduce its capacity to produce oil and gas from the formation. Devicesknown in the art as “sand screens” are typically used to protect suchunconsolidated formations. Sand screens include a structural member,called a “base pipe”, having apertures therein to maintain themechanical integrity of the sand screen (meaning to provide mechanicalsupport for the screen. A “filter layer” is typically disposed outsidethe base pipe. Many different types of filter layer are used, including,for example, wound wire and mesh screen.

More recently, radially plastically deformable sand screens, called“expandable sand screens” have been used in some wellbores to increaseproductivity of wellbores completed in unconsolidated Earth formations.A principal reason for the use of expandable sand screens is tomechanically support the unconsolidated formation prior to initiatingfluid production. By supporting the formation prior to initiatingproduction, it is possible to reduce loss of formation permeability dueto movement of solid materials against the screen during fluidproduction. A conventional (non-expandable) sand screen must necessarilyhave an external diameter smaller than the drilled out diameter of thewellbore (“open hole”) prior to insertion of the sand screen, in orderfor the screen to fit in the wellbore. The smaller screen diameterresults in an annular space between the outer surface of the screen andthe wall of the wellbore, which may become filled with formation solidsmoved from the formation during fluid production. Expandable sandscreens are intended to provide a way to close the annular space priorto beginning fluid production, and thus prevent movement of formationsolids. Expandable sand screens are run into the wellbore in anunexpanded state, wherein the external diameter of the screen is lessthan the drilled out diameter of the wellbore. After insertion, thescreen is expanded using one or more types of expansion tools,preferably to cause the screen to be placed into firm contact with thewellbore wall.

During the expansion of expandable sand screens, it is advantageous topush the sand screen outward to an extent so that it “conforms” to, andapplies pressure to, the wellbore wall in order to hold the sand inplace and increase oil and/or gas flow into the wellbore. Many wellboresmay include sections where the actual diameter of the wellbore exceedsthe drilled out diameter (drill bit diameter) due to washout or othercause. In such sections, it maybe necessary to expand a screen to 35 or40 percent greater than its unexpended diameter in order to place thescreen in form contact with the wall of the wellbore.

One problem with expandable screens known in the art is that they aredifficult to expand more than about 30 to 35 percent because the basepipes made out of carbon steel or stainless steel begin to fail. As aresult, these screens may often not be expanded enough to apply the highcontact pressures needed to hold the sand in place in enlargedwellbores, thus resulting in failure of the sand screen or inadequateproduction. Conversely, if expanded to the degree necessary to provide asuitable amount of contact pressure, the base pipe may be weakened to anextent so as to have very little resistance to crushing under externalpressure, thus leaving the wellbore susceptible to failure.

SUMMARY OF THE INVENTION

It is desirable to have an expandable sand screen that can be made toconform to the wall of a wellbore, even if it is necessary to expand thescreen to 35 percent or more beyond the unexpanded diameter of thescreen, while maintaining sufficient mechanical integrity to resistfailure of the screen and consequent loss of the wellbore.

In one embodiment, a wellbore completion method includes disposing anexpandable screen into a wellbore and disposing a fluid into an annularspace between a wall of the wellbore and the expandable screen. Thefluid contains a plurality of near neutrally-buoyant particles. Themethod further includes radially expanding the screen, whereby the nearneutrally-buoyant particles exert a force against the wall of thewellbore.

Embodiments of the invention may provide a number of technicaladvantages. In one embodiment, placement of neutrally-buoyant ornear-neutrally-buoyant particles in the annular space outside of thescreens makes the screens compliant and allows them to exert a forceagainst the wall of a wellbore and hold the sand particles in place.This facilitates the use of strong base pipe with high torsional, axial,and collapse strength.

Other technical advantages are readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are cross-sectional elevation views illustrating awellbore completion method in accordance with one embodiment of thepresent invention.

DETAILED DESCRIPTION

FIGS. 1 and 2 are cross-sectional elevation views illustrating awellbore completion method in accordance with one embodiment of thepresent invention. Referring first to FIG. 1, a wellbore completionsystem 100 is utilized in completing a wellbore 101 drilled within aformation 102. Wellbore 101 may be drilled using any suitable drillingtechniques and may have any suitable diameter, length, and direction.Formation 102 may be any suitable geological formation; however, thepresent invention is particularly suitable for unconsolidatedformations, such as sandstone.

Holding the sand or other particles from formation 102 in place duringthe completion process is important for effective oil and/or gas flowinto wellbore 101. Thus, expandable sand screens are sometimes utilizedto hold the sand in place. A major problem with prior expandable sandscreens is that they are difficult to expand more than about 30-35%before the base pipes from which they are made begin to fail. Thus,these prior screens may often not be expanded enough to apply highcontact pressures to hold the sand in place.

Therefore, according to the teachings of one embodiment of theinvention, a plurality of near neutrally-buoyant particles 106 aredisposed within an annular space 108 between a wall 109 of wellbore 101and an expandable screen 104 prior to expanding expandable screen 104.Near neutrally-buoyant particles 106 reduce the amount of expansionrequired by expandable screen 104 and increases the contact forcebetween expandable screen 104 and wall 109. In the illustratedembodiment, near neutrally-buoyant particles 106 are disposed within afluid 115.

Expandable screen 104 may be any suitable screen of any suitable sizeand configuration, and may be formed from any suitable material. Forexample, expandable screen 104 may be formed from a suitable carbonsteel and include a fine screen or coarse screen (or both) inside of asuitable sleeve (sometimes referred to as a “shroud”) having suitableapertures formed therein. Expandable screen 104 may also have anysuitable length and may be formed from one or more sections. Ifexpandable screen 104 is formed from more than one section, thenexpandable threads 112 may be utilized to couple the sections together.Expandable screen 104 may be disposed in wellbore 101 by any suitablemethod, such as the utilization of a suitable work string 110. Anysuitable method may be utilized to expand expandable screen 104, such asa cone expander 114 or other suitable expander element.

Near neutrally-buoyant particles 106 may be any suitable particlesformed from any suitable material. As used herein, the term “nearneutrally-buoyant” means that particles 106 each have a density that isequal to or very near the density of fluid 115 in which they aresuspended. As examples, near neutrally-buoyant particles 106 may behollow or low density particles. Although near neutrally-buoyantparticles 106 may have any suitable size and shape, in one embodiment,near neutrally-buoyant particles 106 are generally spherical in shapehaving any suitable diameters. In a particular embodiment of theinvention, the near neutrally-buoyant particles 106 are generallyspherical in shape and have diameters larger than the diameters of thepores existing within formation 102 adjacent wall 109 in order toprevent them from flowing into and plugging the pores in formation 102.With respect to expandable screen 104, in one embodiment, nearneutrally-buoyant particles 106 may be generally spherical in shape andhave diameters larger than the diameters of the holes formed within theoutermost member of expandable screen 104, such as a shroud. In oneembodiment, this prevents the near neutrally-buoyant particles fromdamaging the fine screen inside of the shroud.

Fluid 115 may be any suitable fluid. For example, in one embodiment,fluid 115 is a suitable completion fluid. In addition, fluid 115 may bedisposed within annular space 108 between wall 109 and expandable screen104 in any suitable manner using any suitable equipment, such as a pump.

In some embodiments, fluid 115 develops “gel” strength when it is notbeing circulated. This gel strength allows near neutrally-buoyantparticles 106 to be suspended in fluid 115 even though their densitiesare slightly different than fluid 115. Therefore, in some embodiments,the densities of near neutrally-buoyant particles 106 do not have toequal the density of fluid 115 to be suspended therein.

In one embodiment, some of the near neutrally-buoyant particles 106 eachhave a density slightly greater than fluid 115 such that they tend tofall within fluid 115 prior to expansion of expandable screen 104, andsome of the near neutrally-buoyant particles 106 each have a densityslightly less than fluid 115 such that they will tend to rise withinfluid 115 prior to expansion of expandable screen 104. This may improvethe placement of particles 106 in annular space 108 around screen 104.In another embodiment, near neutrally-buoyant particles 106 each have adensity equal to fluid 115 such that particles 106 substantially remainin place around expandable screen 104 prior to expansion thereof with notendency to rise or fall within fluid 115. Other methods for movingand/or locating particles 106 within fluid 115 are contemplated by thepresent invention. It should be noted that larger near neutrally-buoyantparticles 106 may tend to sink or float faster than smaller particles.Thus, as near neutrally-buoyant particles 106 get larger, the differencein density between near neutrally-buoyant particles 106 and fluid 115may be smaller in order to suspend them in fluid 115.

System 100 may also include a first barrier 118 coupled near a top ofexpandable screen 104 and a second barrier 120 coupled near a bottom ofexpandable screen 104. Barriers 118, 120 may be utilized to confine thenear neutrally-buoyant particles 106 to a particular vertical spacewithin annular space 108 of wellbore 101. Barrier 118 and barrier 120may be any suitable barriers formed from any suitable material, such asan elastomer. Barriers 118, 120 are typically coupled to the outside ofexpandable screen 104 before expandable screen 104 is disposed withinwellbore 101.

A bottom sub 122 may also be coupled to a bottom of expandable screen104 to prevent any fluid 115 from exiting expandable screen 104. Bottomsub 122 may be any suitable plug formed from any suitable material andmay coupled to expandable screen 104 in any suitable manner.

Also illustrated in FIG. 1 is a casing 124, which may case any suitableportion of wellbore 101, and an expandable liner hanger 126 thatfunctions to hang any suitable lining within casing 124. The presentinvention contemplates more, fewer, or different components than thoseillustrated in FIG. 1.

In operation of one embodiment of the invention, and with reference toFIGS. 1 and 2, wellbore 101 is first drilled by any suitable methodwithin formation 102 and the upper portion thereof cased with casing124. Expandable liner hanger 126 is utilized to position expandablescreen 104 within wellbore 101. Work string 110 with cone expander 114coupled thereto is then run-in-hole and fluid 115 is circulated downinto wellbore 101. Fluid 115, with near neutrally-buoyant particles 106suspended therein, fills annular space 108.

Work string 110 then is utilized to apply weight to cone expander 114,which translates downward and starts radially expanding expandablescreen 104, as illustrated best in FIG. 1. Cone expander 114 plasticallydeforms expandable screen 104. As expandable screen 104 is radiallyexpanded out towards wall 109, near neutrally-buoyant particles 106exert a force against wall 109 in order to hold the sand associated withformation 102 in place. In the illustrated embodiment, the nearneutrally-buoyant particles 106 have diameters larger than the poresexisting in formation 102 in order to prevent them from flowing into andplugging the pores. Once cone expander 114 reaches the end of itsdesired travel, then work string 110 and cone expander 114 are pulledout of wellbore 101, thereby leaving the arrangement illustrated in FIG.2.

As shown in FIG. 2, expandable screen 104 is radially expanded outwardtowards wall 109 and applies a force to near neutrally-buoyant particles106 so that they may exert a force on wall 109 of wellbore 101.Expandable screen 104 is thus plastically deformed from a smallerdiameter to a larger diameter. Any suitable expansion is contemplated bythe present invention.

Thus, near neutrally-buoyant particles 106 within annular space 108facilitate expandable screen 104 being compliant and holds sandparticles associated with formation 102 in place by exerting a forceagainst wall 109. This may allow the use of a strong base pipe withexpandable screen 104 with high torsional, axial and collapse strength.Efficient production from wellbore 101 may then be realized.

Although embodiments of the invention and their advantages are describedin detail, a person of ordinary skill in the art could make variousalterations, additions, and omissions without departing from the spiritand scope of the present invention as defined by the appended claims.

1. A wellbore completion method, comprising: disposing an expandablescreen into a wellbore; disposing a fluid into an annular space betweena wall of the wellbore and the expandable screen, the fluid containing aplurality of near neutrally-buoyant particles; and radially expandingthe screen, whereby the near neutrally-buoyant particles exert a forceagainst the wall of the wellbore.
 2. The method of claim 1, wherein thenear neutrally-buoyant particles have a density equal to the fluid suchthat the near neutrally-buoyant particles substantially remain in placearound the screen prior to radial expansion with no tendency to rise orfall.
 3. The method of claim 1, wherein some of the nearneutrally-buoyant particles have a density slightly greater than thefluid density such that they will tend to fall within the fluid prior toexpansion and some of the near neutrally-buoyant particles have adensity slightly less than the fluid density such that they will tend torise within the fluid prior to expansion.
 4. The method of claim 1,wherein the near neutrally-buoyant particles comprise generallyspherical particles having diameters larger than the diameters of thepores existing within a formation associated with the wall of thewellbore.
 5. The method of claim 1, wherein the fluid comprises acompletion fluid.
 6. The method of claim 1, further comprising placing abarrier in the annular space near a top of the screen.
 7. The method ofclaim 1, further comprising placing a barrier in the annular space neara bottom of the screen.
 8. A wellbore completion system, comprising: anexpandable screen configured to be disposed into a wellbore; a fluidcontaining a plurality of near neutrally-buoyant particles; a pumpoperable to dispose the fluid into an annular space between a wall ofthe wellbore and the expandable screen; and an expander operable toradially expand the screen when disposed within the wellbore, wherebythe near neutrally-buoyant particles exert a force against the wall ofthe wellbore.
 9. The system of claim 8, wherein the nearneutrally-buoyant particles have a density equal to the fluid such thatthe near neutrally-buoyant particles substantially remain in placearound the screen prior to radial expansion with no tendency to rise orfall.
 10. The system of claim 8, wherein some of the nearneutrally-buoyant particles have a density slightly greater than thefluid density such that they will tend to fall within the fluid prior toexpansion and some of the near neutrally-buoyant particles have adensity slightly less than the fluid density such that they will tend torise within the fluid prior to expansion.
 11. The system of claim 8,wherein the near neutrally-buoyant particles comprise generallyspherical particles having diameters larger than the diameters of thepores existing within a formation associated with the wall of thewellbore.
 12. The system of claim 8, wherein the fluid comprises acompletion fluid.
 13. The system of claim 8, further comprising abarrier coupled near a top of the screen.
 14. The system of claim 8,further comprising a barrier coupled near a bottom of the screen. 15.The system of claim 8, wherein the expander comprises a cone expander.16. A method for expanding an expandable screen within a wellbore,comprising: disposing a fluid containing a plurality of nearneutrally-buoyant particles into an annular space between the expandablescreen and a wall of the wellbore; and expanding the screen in such amanner that the near neutrally-buoyant particles exert a force againstthe wall of the wellbore.
 17. The method of claim 16, wherein the nearneutrally-buoyant particles have a density equal to the fluid such thatthe near neutrally-buoyant particles substantially remain in placearound the screen prior to expansion with no tendency to rise or fall.18. The method of claim 16, wherein some of the near neutrally-buoyantparticles have a density slightly greater than the fluid density suchthat they will tend to fall within the fluid prior to expansion and someof the near neutrally-buoyant particles have a density slightly lessthan the fluid density such that they will tend to rise within the fluidprior to expansion.
 19. The method of claim 16, wherein the nearneutrally-buoyant particles comprise generally spherical particleshaving diameters larger than the diameters of the pores existing withina formation associated with the wall of the wellbore.
 20. The method ofclaim 16, further comprising defining a cylindrical volume for the nearneutrally-buoyant particles by placing a first barrier in the annularspace near a top of the screen and a second barrier in the annular spacenear a bottom of the screen.